Phosphorus boron compounds



United States Patent*() "ice i all 3,100,774 PHOSPHORUS BGRON COMPOUNDS Theodor. Reetz, Webster Groves, Mm, assignor to Monsanto Chemical Company, St. Louis, Mo.,. a corporation of Delaware i No Drawing. Filed July 29, 1 959, Ser; No. 830,197

20 Claims. (Cl. 260-223) This inventionrelates to a new class of phosphorus boron compounds and to the method ot preparing the same. Moore particularly, it is concerned with new com bound to the trivalent phosphorus atom which supplies the necessary electrons for the bond.

It is therefore an objectof this invention to provide new nitrogen "containing phosphorus boron compounds. It is a further object to providephosphorus boron compounds which exhibit av surprising degree of stability. Still a further object is to provide a method for the preparation of these novel nitrogen containing phosphorus boron compounds. These and other objects, advantages and features of the invention will become apparent upon consideration. of the following description thereof.

The structural formula of the new compounds of this invention is: r r l m 11X i Xu where X. X and X are like? or unlike amine radicals selected from the group consisting of r I hydrogen provided that no, more than one hydrogen be bonded to anyone nitrogen atom. Illustrative, but not limitative, of the organic radicals represented by'R and R are the alkyl radicals, such asmethyl, ethyLpropyl, isopropyl, butyl, hexyl, -octyl, dodecyl, .fl-chloroethyl', 2- methylpentyl, 2-ethylhexyl, etc.; unsaturated aliphatic radicals such as propenyl, butenyl,,etc.; arylrradicals such 3,lll0,774 Patented Aug. 13, 1963 methylene and pentamethylene, the nitrogen rings, the

. hydrogen atoms on said rings may be substituted by an centlyreported by Kodama.

asfphenyl, napthyl, etc; substituted aryl radicals such as chlorophenyl, 2,4dibrom'ophenyl, ethylphenyl, etc.; aralkyl radicals such as benzyl, phenylethyl; etc;; alicyclic radicals suchlas cyclohexyl, cyclopentyl, etca; andhetro' cyclic radicalswsuch. as furyl, furfuryl, thienyl, etc. A

preferred embodiment of, this inventioniconsists'f of those 1 r compounds wherein R and R are selected from the group consisting of hydrogen and alkyl radicals containing from i l to 12 carbons provided that no more thanrone hydrogen atom be bonded. to any one nitrogen atom. It should. also be noted that in the case of the tetra- However, the compounds of'this invention are phosphorous triamide boranes having a hydrocarbon radical substituted for at least one hydrogen on each nitrogen atom and display a markedly superior stability. Of the known compounds containing the RH, group, perhaps the most stable are the trialkylamine boranes of which trimethylamine borane is a noteworthy example. it has been determined that the borine containing compounds disclosed herein are considerably more stable as evidenced by the following experiments. i r

When trimethylamine borane is mixed in a closed system with hexamethyl phosphorous triamide in equimolar amounts at room temperature, the conversion is in excess of according to the following equation:

When trimethylamine borane is treated with concentrated hydrochlorici acid and methanol (1:1), two hours about of the product is decomposed. In the case of hexamethyl phosphorous triamide borane, only about 18% decomposition occurs under the same conditions. The following test is also illustrative of the greater stability of these phosphorus boron compounds in comparison with trimethylamine borane. N,N,N"-(tetramethylene) phosphorous triamide borane can be, precipitated from a solution thereof in concentrated hydrochloric acid, by dilution with water and recovered unchanged. Under the same conditions, trimethylamine b orane is completely decomposed with strong evolution of hydrogen. I H

In accordance with this invention the new compounds are prepared from phosphorous triarnides of the formula 40 i j p eg sodium, potassium, etc. borohydride, when employed in the presence of such promoters as (a) carbonyl containing compounds, (b) organic acids, and (c) inorganic acids. Suitable carbonyl containing compounds include carbon dioxide, ketones such as dimethyl ketone, diethyl ketone and the like, aldehydes such as acetaldehyde, isobutyraldehyde and the like, and esters such as ethyl acetate, methyl propionate and the like. Inorganic-acids such as hydrochloric, hydrobromic and hydrofluoric and organic acids suchras formic, acetic, butyric, v-aleric and the like are also suitable. Illustrative of the reactions which take place are the following:

N BHr+P[Means-F 05 HCOONa+H BP[N(CH3)2]3 (Ketonel NaBH4+ 1 N o:u,); 3+ 0:0

j CH:

C-O Na ninrrmonmls i vessel at the end of the reaction.

3 (Organic acid) NaBH +P [N (CH 3 are reacted with the borine releasing compounds will vary. depending upon the nature of the latter. With the (Inorganic acid) trialkylamine boranes, temperatures from 20 to 120 C..

may be employed, the preferredrange-being from 70 to 100 C. In the case of diborane lower temperatures ranging from 30 to 60 C. are more desirable. When metallic borohydrides are employed temperatures may vary from '40 to 100 C., and usually the reaction is carried out in the presence of other as a solvent, as, for example, ethyl ether, dioxane', tetrahydrofuran and the like. 1

The invention will be more fully understood by reference to the following examples which provide an indication of suitable reactants, solvents, and the proportions of each as well as temperatures to be used in preparing the novel nitrogen containing phosphorus boron compounds. These examples, however, are given for the purpose of illustration only, and are not to be construed as limiting the scope of the present invention in any way.

EXAMPLE I Hexamethyl Phosphorous T riamide Borane HsBP[N(CHa) ]s I A mixture of 3.64 grams of trimethylamine borane and 8.20 grams of hexamethyl phosphorous triamide was heated with stirring up to 90 C., maintained at that temperature for about 20. minutes, and then raised to 110 C. and held there :for a short time. At 70-80 C. a moderate, and at 90 C. a strong, evolution of trimethylamine was observed. 2.6 grams (88% of theory).of trimethylamine was condensed in a trap. The reaction product, 9.2 grams, was distilled at 6l63 C./0.5 mm. The distillate was dissolved in dioxane. Addition of water to the dioxane solution caused an oily product to separate. This oily product became crystalline on standing for a short time. It was then dried and distilled. One fraction, B.P. 49-50 C./0.1 mm. was taken. It

was identified as hexamethyl phosphorous triamide borane; M.P. 32.5 C. g

p 7 EXAMPLE. II

g H examethyl. Phosphorous Tridmide Borane H BP[N(CHa)]s V A solution of 14.56 grams of trimethylaminefborane and 35.8 grams of hexamethyl phosphorous triarnide in 50 ml. of dioxane was gradually heated to about 112 C.

trimethylamirre was observed at 8590 C. Nitrogen was. passed'slowly through the contents of the reaction 11.0 grams (93% of theory) of trimethylamine was collected in a trap. The reaction product was filtered and dilute hydrochloric acid added to the filtrate to remove the excess hexamethyl phosphorousniamide'and to dissolve the dioxane'. An 'oil precipitated and became crystalline on standing. The

crystallineproduct was separated by filtration, washed withwater and dried. There was obtained 30.5 grams (86% of theory) of hexamethyl phosphorous triamide borane; M.P. a

j, EXAMPLE nt 7 Hexamethyl Phosphorous Triamide Borane rrsnrrmcnmn i Diborane was generated as follows according to Schlesingers method (JACS 75, 1953, pp. 202-207). 29.75 grams of boron fluoride etherate diluted with 30 ml. of ether were added to a stirred mixture of 5.7 grams "of sodium .borohydride and 80 ml. of tetrahydrofur'an in a flask at 40 C. in about 45 minutes. Then the reaction mixture was heated gradually to about 58 C. Nitrogen was then passed slowly through the contents of the flask.

The diborane evolved was introduced into another flask which contained a solution of 35 grams of'hexamethyl phosphorous triamide in 50 ml. of tetrahydrofuran. Vigorous stirring and cooling at about 20 was maintained. After all of the diborane was introduced, the reaction mixture was heated to room temperature, and then most of the solvent was stripped ofiby distillation. Then a sufiicient amountof dilute hydrochloric acid was added to dissolve the remaining solvent and the excess hexam'ethyl phosphorous triamide. The oil which separated crystallized on standing. The crystalline product was filtered and dried on air. There was obtained 31.6 grams (89 of theory) of hexamethyl phosphorous triamide borane;

M.P. 32.5 C.

EXAMPLE IV Hexamethyl Phosphorous Triamide Borane HsBP[N(CHa) ]s Carbon dioxide was gradually introduced at C. into a stirred mixture of 17.9 grams of hexamethyl phosphorous triamide, 3.78 grams of sodium borohydride and 50 7 ml. of tetrahydrofur'an until the reaction was completed and no further earbondioxide was absorbed. The reaction product was treated with sufficient dilute hydrogen chloride to precipitate an oily product and dissolve the excess hexamethyl phosphorous triamide as wellas the solvent. The oily product was taken'up with hexane and filtered from a small amount of yellow insoluble solid present therein. The filtrate was evaporated, andthe within about 90 minutes. A rather rapid evolution of residue was dissolved in dioxane. The addition of water to this solution caused an oil to precipitate which became crystalline'upon standing. Thecrystalline product was filtered and dried. A yield of 11.5 grams (65% of theory) of hexamethyl phosphorous triamide borane was obtained.

EXAMPLE V Hexaethyl Phosphorous Triamide Borane g HaBP[-N(C H5)2]s Diborane was generated from the reaction of '15 .5 grams of boron fluoride etherate, 3.4 grams of sodium borohydride and 70 m1. of tetrahydrofuran (see Example III). The diborane thus generated was introduced into a flask and reacted with 24.7 grams of hexaethyl phosphorous triamide dissolved in 50 ml. of'tetrahydrofuran. Throughout the reaction, vigorous stirring anda. temperature of about 10 C. were maintained. The flask was then shaken with dilute hydrochloric acid to destroy and dissolve any unreacted hexaethyl phosphorous triamide. An oil precipitated which was Washed with water and dried in a vacuumv (5 mm. of Hg) at-60-70" C. A yield of 22.5

, grams (86% of theory) of, hexaethyl phosphorous trigrams'of boron fluorideetherate, 4.1 grams of sodiuni' borohydn'deand 70 ml. of tetrahydrofuran (see Example III). The diborane' so generated was introduced into "a flask containing 41.5 grams of hexa-n-butyl phosphorous triamide and 30 of tetrahydrofuran. The reaction mixture wasstirred vigorously, and .a temperature of 25-30. C. .Was maintained. The mixture was then' tr'eated i with suflicient dilute hydrochloric acidto dissolve the solvent and destroy any excess of'hexa-n butyl:phosphor= Y t ous triamide. oily product separated and was washed with dilute solution of sodium sulfate.) Said productwas then separated from the solution and subjected to 'vacuum (4 mm.- of Hg) at about C; There was obtained 39.5 grams (92% of theory) of hexa-n-butyl phosphorous triamide borane.

EXAMPLE VII N,N,N-(Tetramerhylene) Phosphorous Triamz'de Borane phosphorous triarnide. A white crystalline precipitate appeared and was dissolved in concentrated hydrochloric acid and precipitated by the addition of water. The latter precipitate was then filtered, washed with water, and dried in vacuum. A yield of 4.8 grams (94% of theory) of N,N,N"-(tetramethylene) phosphorous triarnide borane was obtained; M.P. 59 C.

EXAMPLE VIII Hxomethyl Phosphorous Tridmzde Borane HsBP[N(CHs) ]s A solution of 3 grams oflwater and 12 grams of acetone was added portionwise. to a mixture of 1.9 grams of sodium-borohydride,;9. grams of hexamethyl phosphorous triarnide and 27 ml. of tetrahydrofuranwi'th vigorous stirring at about 27 C. over a period of three hours. The mixture was then heated at about 55 C. for 30 minutes, after which 25 ml. of water was added dropwise at 40 C. The resulting reaction mixture was rendered acidic with dilute hydrochloric acid and stirred until the unreacted hexamethyl phosphorous triamide was destroyed. An oil precipitated and became crystalline on cooling. The white crystalline product was filtered, washed with water and dried on air. There was obtained 4.7 grams (53% of theory) of hexamethyl phosphorous triamide borane i BXAMPLEIX Hexamethyl Phosphorous T riamide Borane 3" grams of acetic acid "dissoliied in 10ml. of tetrahydrofuran was added dropwise to a mixture of l.9-grams of sodium borohydride and 25 ml. of tetrahydrofuran at -2.0 to 30 C. with vigorous stirring over a' period of 45 minutes. When the evolution of hydrogen ceased, 12 grams t hexamethyl phosphorous tr-iamide was added to thereactiontnixture at ab'outtl C. This reaction mixture was then stirred at room temperature tor about 3 hburS ahdlat about. 60- C. for an additional hour.

.:wasusevapor ated, leaving an oily residue. which was then treated with a small amount of water. The oil became crystalline on standing, and the crystalline product was recovered by filtration, washed with water and dried on air. There was obtained 4.1- grams (46% of theory) of r hexamethyl PhOSPhOI'OHSltl'lflIIlldG borane.

H examethyl Phosphorous Triamide Borane HsBP [N (CH3) a A solution of 1.82 grams of hydrogen chloride dissolved in ml. of tetrahydrofuran was added to a mixture of 1.9 grams of; sodium borohydride and 25 m1. of

tetrahydrofiuran at about 60 C. within a period of onehour. .:When 'the evolution of hydrogen ceased, 12

grams of hexamethyl phosphorous tria-mide was added. The reaction mixture was slowly heated to room temperature and maintained at that point for about 2 hours. *It was then heated for one additional hour at about 45 C. The reaction mixture was 'then treated with sufiicient dilute hydrochloric acid to hydrolyze the excess of hexamethyl phosphorous triamide and dissolve the solvent.

,Hexanewas then added and the resulting mixture shaken.

A small amount of a yellow precipitate was formed which was insoluble in hexane and was removed by filtration. The filtrate was evaporated, and the residue crystallized. There was obtained 5.6 grams (63% of theory) of hexamethyl phosphorous triamide borane.

In addition to the boranes prepared in the preceding examples, the following boranes are further. illustrative of compounds coming within the scope of this invention:

Hexapropenyl phosphorous triamide borane N,N',N-(trimethyl) phosphorous triamide borane Hexa-B-chloroethyl phosphorous triamide borane Hexabenzyl phosphoroustriamide borane Hexacyclohexyl phosphorous triamide borane N,-N',N- (tridodecyl) phosphorous triamide borane Hexaphenyl phosphorous triamideborane Tris (N-phenyl, N-methyl) phosphorous triamide borane Tris (N-benzyl, N-ethyl) phosphorous triamide borane N,N,N"-(triphenyl) phosphorous triamide borane Tris (N-octyl, N-ethyl) phosphorous triamide borane Tris (N-tolyl, N-methyl) phosphorous triamide borane The novel boranes of this invention display considerable utility and are of particular value as gasoline additives for the prevention of preignition. By way of example, tricresyl phosphate, a well-known pre-ignition suppressant, has been found to be only as effective as certain of the compounds of this invention with regard to preignition prevention. In addition, the new compounds of the invention-find utilityas anti-oxidants and as polymer zationcatalysts. They are also useful as. blowing agents inepoxy resins representative of which would be the reaction product of bis(4-liydroxyphenyl) -2,2-propane 4. N,N,N" (tetramethylene) phosphorous triamide borane. 5. The process of preparing a compound of the formula X H313 P X where X, X and X"each represent a member of the group consisting of omeonz on, OKs-Cg: wherein R and R each represent alkyl of from 1 to 12 vcarbon atoms, which compi ises reacting a corrip'ound of the formula X P X "where X, X and X have the same meaning as above with a borine group releasing compound selected from the group consisting of rtrialkylamine boranes, boron hydrides and metal borohydr-ides. 7

6. The process of preparing a compound of the formula H313 P X I \X,! where X, X and X" each represent a member of the group consisting of wherein R and R each represent alkyl of from 1 to 12 carbon atoms, which comprises'reacting a compound of the formula I 3 1 GHQ-CH2 I /GH2CEI CHr-CH: I wherein R and R each represent alkyl of from 1 to 12 carbon atoms, which comprises reacting a compound of the formula I a XII where X, X and X have the same meaning as above with a boron hydride. I

8. The process of preparing a compound of the formula carbon atoms,

and

8 where X, X and X each represent, amember of. the group consisting of r C Hz-C Hi QH:(J112 and CHi-CHI CH1 1 H k wherein R and R each represent jalkYl of'from -1 to'IZ carbon atoms, which comprises reacting a compound of the formula where X, X and X have the samemeaning as above with trimethyl-amine borane.

9. The process of preparing a compound of the formula X Ha B P X where X, X and X each represent a member of the group consisting of CHI-CH1 CHPCHI and CHE-CH1 OH: CHz-Cfig wherein R and R each represent alky l of from lto 12 which comprises reacting a compound of the formula r I where X, X and X have the same meaning a ab v with diborane. i 1 r 10. The process of preparing a compound of the formula. 1 I

fizBP x where X, X and X each group consisting of C Hie-CE:

2 0155-052 -N\' on: I I GHQ-0 I represent a meniber of the.

wherein R and" R each represent alkyl of from 1 to '12 carbon atoms, which comprises reacting a compound of the formula "where XQX and X have thesame meaning as above where X, X and X" each, represent a member of the group consisting of whereinR and R each represent alkyl of from 1 to 12 carbon atoms, which comprises reacting a compound of the formula t where X, X and X have the same meaning as above CH2CH2 CHr CH:

and

0112- 2 GH2 CHPC 2 wherein Rand R each represent alkyl of from 1 to 12 carbon atoms, which comprises reacting a compound of the formula where X, X and X" have the same meaning as above 10 with sodium borohydride and hydrochloric'acid in the presence of an inert solvent. r

13. Hexabenzyl phosphorous triamide boran 14. Hexaphenyl phosphorous triamide borane. 15. Tris(N-pl1enyl, N-methyl) phosphorous triamide borane.

16. Hex'acyclohexyl phosphorous triamide borane. 17 i A compound of the formula where-R and R are each alkyl of from 1 to 12 carbon atoms.

18. N,N,N"-(pentamethy1ene) phosphorous triamfide borane.

19. A compound of the formula /X HzBP X XII where X, X and X each represent a member of the group consistingof CHz-CHa CH2CH2 and CHz-OH: --N\ /CH:

OHa-QH: wherein R and R are each selected from the group consisting of hydrogen, alkyl and mono and dihaloailkyl of from 1 to 12 carbon atoms, cycloalkyl and mono and dihalocycloalkyl of from 5 to 6 carbon atoms, monocyclic aromatic hydrocarbon of up to 8 carbon atoms and mono and dihalomonocyclic aromatic hydrocarbon of up to 8 carbon atoms, benzyl and mono and diahalobenzyl and naphthyl and mono and dihalonaphthyl, the halogen atoms of said mono and dihalo groups being selected from the group consisting of chlorine and bromine, provided that at least one of R and R must be. other than hydrogen. 7

20. The process of preparing a compound of the formula,

where X, X and X each represent a member of the group consisting of ,wherein R and R each represent alkyl of from 1 to 12 11v 12' carbon atoms, 1 which comprises reacting a compound acids hydrohalic acids and saturated carboxylic acids of of the formula, 1 to 5 carbon atoms.

v I X V Pgx' References Cited in the file of this patent X' 5 Bergmann: The Chemistry of Acetylene and Related C d 80, l r l h N Where X and ,X" have the same meamng as above, ZE E S page h-ltrsclenge Pub ers Inc 6w with a metal borohydride and. a promoter selected from v Y [the class consisting of carbon dioxide, dialkyl ketones, Kadama' merfcanchmwal soclety s of alkyl 'aldehydes, alkyl esters of saturated carboxyl-ic 10 Papers 1 m m 9 

18. N,N'',N"-(PENTAMETHYLENE) PHOSPHOROUS TRIAMIDE BORANE.
 19. A COMPOUND OF THE FORMULA 